Apparatus for positive displacement bonding

ABSTRACT

Apparatus for positive displacment bonding and, more particularly, for automatically forming, on a continuous, reproducible basis, fusion bonds devoid of structural, electrical and cosmetic defects between two or more workpieces by moving a heated electrode into the area to be bonded so as to uniformly heat and melt the portions of the workpieces to be bonded while, at the same time, displacing substantially all of the molten material from the area to be bonded into a storage area or reservoir surrounding the heated electrode where such molten material is maintained in its uniformly heated molten state, then retracting the electrode so as to permit the molten material to return to the cavity formed by the electrode in the workpieces where such molten material is allowed to cool and solidify, thus forming a flawless bond between the workpieces, and then repeating the foregoing steps to bond the previously bonded parts to yet another workpiece-thermal or fusion bonds are made in accordance with the methods of the invention by a combination of (1) elevated temperature levels sufficient to melt the material to be bonded, and (2) displacement of the molten material; as contrasted with more conventional techniques and/or apparatus which combine elevated temperature levels and pressure.

United States Patent 1 1 Schenk, Jr. et al.

1 APPARATUS FOR POSITIVE DISPLACEMENT BONDING [73] Assignee: Gould Inc., St. Paul, Minn.

[22] Filed: Jan. 21, 1974 [21] Appl. No.: 435,180

[52] U.S. Cl.'. 164/80; 29/498; l64/DIG. l; 219/86; 228/45 [51] Int. Cl.- ..I-I01M 2/22; HOlM 2/30; B22D 19/00; 823K 11/00 [58] Field of Search 164/80, 107, 108, 110,

l64/DlG. 1; 29/486, 498, 491, 472.1, 204, 475, 494, 495' 228/45, 58; 136/176, 134 R, 168; 219/78, 86

Primary E.\'aminerFrancis S. Husar Assistant E.\'uminerCarl Rowold Attorney, Agent, or FirmWolfe, Hubbard, Leydig, Voit & Osann, Ltd.

[451 Sept. 30, 1975 5 7 ABSTRACT Apparatus for positive displacment bonding and, more particularly, for automatically forming, on a continuous, reproducible basis, fusion bonds devoid of structural, electrical and cosmetic defects between two or more workpieces by moving a heated electrode into the area to be bonded so as to uniformly heat and melt the portions of the workpieces to be bonded while, at

the same time, displacing substantially all of the molten material from the area to be bonded into a storage area or reservoir surrounding the heated electrode where such molten material is maintained in its uniformly heated molten state, then retracting the electrode so as to permit the molten material to return to the cavity formed by the electrode in the workpieces where such molten material is allowed to cool and solidify, thus forming a flawless bond between the workpieces, and then repeating the foregoing steps to bond the previously bonded parts to yet another workpiecethermal or fusion bonds are made in accordance with the methods of the invention by a combination of l) elevated temperature levels sufficient to melt the material to be bonded, and (2) displacement of the molten material; as contrasted with more conventional techniques and/0r apparatus which combine elevated temperature levels and pressure.

5 Claims, 23 Drawing Figures US. Patent Sept. 30,1975 Sht 1 of13 3,908,742

(ff/ii 41f) US. Patent Sept. 30,1975 Sheet4of13 3,908,742

U.S. Patent Sept. 30,1975 Sheet60f13 3,908,742

U.S. Patent Sept. 30,1975 Sheet7of 13 3,908,742

US. Patent Sept. 30,1975

Sheet 11 of 13 US. Patent Sept. 30,1975 Sheet 12 0f13 3,908,742

U.S. Patent Sept. 30,1975 Sheet 13 of 13 3,908,742

APPARATUS FOR POSITIVE DISPLACEMENT BONDING RELATED APPLICATIONS Robert l-lolbrook Cushman, Ser. No. 435,157, filed Jan. 21, 1974.

Raymond L. Schenk, Jr., Ser. No. 435,178, filed Jan.

Alan S. Keizer, Ser. No. 435,179, filed Jan. 21, 1974.

Robert Holbrook Cushman and Raymond L. Schenk,

Jr., Ser. No. 435,179, filed January 21, 1974.

Raymond L. Schenk, Jr. and Alan S. Keizer, Ser. No.

435,160, filed Jan. 21, 1974.

Kurt R. Stirnerand Robert Holbrook Cushman, Ser.

No. 435,172, filed Jan. 21, 1974.

Raymond L. Schenk, Jr., and John A. Bruzas, Ser.

No. 435,181, filed Jan. 21, 1974.

Raymond L. Schenk, Jr., John A. Bruzas and William E. Coville, Ser. No. 435,182, filed Jan. 21, 1974.

John A. Bruzas and William E. Coville, Ser. No.

435,156, filed Jan. 21, 1974.

Raymond L. Schenk, Jr. and William B. Hayes, Ser.

No. 435,166, filed Jan. 21, 1974.

BACKGROUND OF THE INVENTION The present invention relates in general to'fusion bonding or thermo bonding of two or more workpieces and, more particularly, to apparatus characterized by its ability to automatically form, on a continuous, reproducible, high speed, production-line basis, fusion bonds devoid of structural, electrical and/or cosmetic defects between two or more workpieces by a technique hereinafter referred to as positive displacement bonding." In its principal aspects, the invention is concerned with improved apparatus for automatically moving a heated electrode through the portions of the workpieces to be bonded so as to uniformly heat and melt those portions of the workpieces to be bonded while, at the same time, displacing the molten material into a storage area or reservoir surrounding the heated electrode where such material is maintained in its uniformly heated molten state while further movement of the electrode into the workpieces creates a cavity therein, thereafter, retracting the heated electrode so as to permit the molten material to return to the cavity formed by the electrode in the workpieces where such molten material is allowed to cool and solidify, thus forming a flawless bond between the workpieces, and then repeating the foregoing steps to permit bonding of still other workpieces to the previously bonded parts.

In recent years, there has been an ever increasing trend toward, and demand for, automation and mechanization in virtually all branches of industry. In many industries, typically including, but not limited to, the battery making industry, it is often necessary to bond two or more workpieces together to form a unitary assembly wherein the bond is characterized by its structural strength and/or, in some instances, by excellent characteristics of electrical conductivity. Various methods have been devised for bonding such work pieces together including, merely by way of example, welding, thermo-compression bonding, ultrasonic bonding, percussion welding, etc.

The particular technique selected has heretofore de-.. pended upon many variable parameters, including: 1) the sizes and/or shapes of the workpieces; and (2) various characteristics of the particular -materials to be bonded which may vary widely in such areas as electrical and/or thermal conductivity characteristics, melting points, etc. Moreover, the particular technique employed has often been dictated by physical limitations in access to the region where the bonds are to be effected. Merely by way of example, in the battery industry it is often necessary to bond two or more pieces of led together at various points, in some cases internally and in others externally of a given battery cell. Lead, of course, is characterized by having a relatively low melting'point on the order of only 630F., as contrasted with, for example, steel which has a melting point on the order of 3,000F. Moreover, where the lead work- 'pieces comprise battery straps, plates, terminal posts and/or intercell connectors, such as commonly employed in industrial motive-powder batteries, automotive batteries, and the like, it is often difficult to gain access to the parts to be bonded. Even where access can be obtained, one is normally limited in the amount of heat that can be applied and in the types of reducing agents that can be utilized by virtue of other components present in the area of the bond to be effected such, for example, as the battery casing or cell jar which is commonly made of rubber, the electrolytic acids present in or to be added to the battery cells, the pasted positive and/or negative plates, the separators which are commonly made of microporous rubber, etc. Many efforts have been made to devise improved bonding techniques which can be universally applied for the purpose of bonding two or more workpieces together irrespective of the wide range of variable parameters mentioned above. Moreover, consistent with the demands of industry today, numerous efforts have been made to devise bonding techniques which are capable of automation so as to enable automatic bonding of multiple workpieces as an integrated part of massproduction line and/or assembly line techniques. Typical of the aforementioned approaches are those described in US. Pat. Nos. 3,591 ,755, 3,608,809 and 3,706,126 of Robert l-lolbrook Cushman, assigned to the Western Electric Company, and relating to mechanical-thermal-pulse continuous fusion bonding processes and apparatus which are. based, at least in part, upon a combination of applied and controlled pressure and temperature to effect a desired bond.

However, despite all such prior efforts which have met with varying degrees of success, certain industries have continued to employ the more tedious, timeconsuming, manual bonding techniques which have been known and utilized for many years. Typical of these is the industrial motive-power battery industry where lead-to-lead bonds are still almost universally made by hand-torching or hand-burning techniques employing oxyacetylene torches and/or carbon burning tools. These techniques require highly skilled artisans who are capable of forming satisfactory .bonds only after considerable training and, even then, a relatively high percentage of the bonds formed are not capable of meeting the rigorous quality control standards set by the battery industry. Typical of the types of difficulties encountered even by such skilled artisans are: 1 nonuniform heating of the interface between the parts to be bonded resulting in no bonding at all at some locations, and/or burn-out of connectors and/or other parts because of overburning, thereby destroying the connector or other parts; (actual damage to and/or destructionof the rubber casing or battery cover due to inadvertent direct application of the flame or carbon tip thereto; (3) lack of control over, and resultant nonuniformity of the depth of, bond penetration into the parts to be bonded, thereby resulting in bonds which are unsatisfactory from either or both of structural and- /or electrical conductivity characteristics; and (4) substantially complete melting of one of the two or more parts to be bonded accompanied by failure to melt the surface of a second of the pieces to be bonded, thereby resulting in a cold-knit between the properly and improperly melted pieces.

As a direct result of the inability of certain industries -for example, the battery industryto utilize the aforementioned known automatic and semi-automatic bonding systems, and the continued industry-wide reliance on hand-torching and/or hand-burning techniques, numerous disadvantages have continued to plague such industries. More specifically: (1) various industries, at great expense to themselves, have had to continue to attempt to train personnel in the difficult, time-consuming hand-torching or hand-burning techniques; (2) as a result of the relatively high heat generated by such techniques, the use of low melting point, economical, lightweight plastic battery casings has been precluded; (3) the percentage of batteries and/or battery cells rejected because of unsatisfactory bonds has remained high; and (4) the number of batteries which have passed rigorous quality control tests and/or procedures while having latent defects in the bonds has been unacceptably high, resulting in customer dissatisfaction because of the presence of leakers," particularly in the battery post/intercell connector, as well as an extremely objectionable phenomenon known in the art as electro-capillary action wherein battery electrolyte is actually pumped out of the battery cell through minute passages passing through the positive battery post/connector interface where the bond is de fective, thereby not only weakening the cell affected and decreasing its life and usefulness, but often creating a direct short which drains the battery and which often causes corrosion and irreparable damage to other equipment in the immediate area.

OBJECTS OF THE INVENTION It is a general aim of the present invention to provide improved bonding apparatus which overcomes all of the foregoing disadvantages and which is characterized not only by its dependability and reliability in operation, but, also by its ability to continuously reproduce successive bonds having substantially identical characteristics and which meet the rigorous quality control standards set by the industry. More specifically, it is a principal aim of the invention to provide new and novel apparatus for forming metal-to-metal bonds which, when applied to the battery making industry, substantially eliminates, if not completely eliminates, the danger of leakers and/or electro-capillary action resulting from non-uniform bonding of the battery post/intercell connector interface.

Another of the general objectives of the present invention is the provision of improved bonding apparatus which can be readily introduced into existing production and/or assembly lines with only minimum-revisions to, and interruption of, such lines.

A further object of the invention is the provision of improved apparatus for producing bonds between two or more components wherein each bond-produced is characterized by the uniformity of the bond through any desired, preselected depth into the workpieces, thereby producing bonds which, in the battery field, are devoid of leakers and devoid of electro-capillary action.

In one of its most important aspects, it is an object of the present invention to provide an improved positive displacement casting system which permits rapid modification of the head to form structurally and/or electrically sound uniform bonds between two or more components which must subsequently be bonded to still other components in a later assembly operation, yet which permits use of the existing bonding system with only minimum changes thereto.

These and other objects and advantages of the present invention will becomemore readily apparent .upon reading the ensuing detailed description of the invention and upon reference to the attached drawings.

I DESCRIPTION OF THE DRAWINGS FIG. 1 is a fragmentary exploded perspective view, here illustrating the various components present in a conventional lead-acid storage battery cell of the type commonly manufactured today and for many years past in the industrial motive-power battery industry.

FIG. 2 is a fragmentary perspective view, here illust'rating the conventional and well-known technique of bonding an intercell connector with the use of a handheld carbon burning tool and a hand-held source of supplemental lead.

FIG. 3 is a vertical side elevation, partly in section, of a conventional battery cover, post, bushing and intercell connector assembly, here illustrating the parts prior to a hand-torching or hand-burning bonding operation.

FIG. 4 is a perspective view of a portion of a positive displacement bonding system suitable for use with the present invention, here illustrating an industrial motive-power battery disposed on a conveyor beneath a bonding head positioned to automatically effect a bond between a lead battery post of one battery cell and an intercell connector.

FIG. 5 is a fragmentary perspective view taken generally at right angles to the view shown in FIG. 4 and here depicting other portions of the apparatus.

FIG. 6 is a plan view of the exemplary apparatus shown in FIG. 4, here depicting the bonding head over one conveyor belt and a battery positioned on the adjacent conveyor belt in readiness for a bonding operation.

FIG. 7 is an elevational view taken substantially along the line 7-7 of FIG. 6, here depicting the bonding head in solid lines disposed over a battery carried by the lefthand conveyor and in phantom lines over a battery carried by the right-handconveyor.

FIG. 8 is a perspective view of the front of a control console utilized with the apparatus of the present invention, here depicting the console with its lower door open to expose the drawer containing certain of the electrical controls for the system.

FIG. 9 is an exploded perspective view, here illustrating particularly the relationship between a battery cover, post, bushing and intercell connector emgodying featuresof the present invention.

FIG. l0-is an elevational view, partly in section, similar to FIG. .3, but here illustrating the various components of a typical battery post/intercell connector assembly embodying features of the present invention, again depicting the parts prior to a bonding operation.

FIGS. 11a through lle are fragmentary, enlarged, simplified, and somewhat diagramatic side elevational views, partly in section, here depicting the sequence of operations in a typical positive displacement bonding operation; FIG. 11a depicting the battery components to be bonded with the bonding head disposed above such components; FIG. 11b illustrating the bonding head properly located and locked in position in readiness to initiate a bonding operation; FIG. 11c illustrating the component parts of the system with the bonding ram-like electrode partially advanced into the workpieces to be bonded, and with the molten lead formed through this stage of the procedure having been displaced into surrounding relationship to the ram; FIG. 11d illustrating the component parts of the system with the ram-like electrode fully advanced into the workpieces to be bonded and with the molten lead formed having been displaced into surrounding relationship to the ram; and, FIG. lle depicting the component parts of the system with the bonding head still in its down position but with the ram-like electrode retracted and with the molten lead having been returned to the cavity formed by the ram in the workpieces and having cooled and solidified to form a finished bond.

FIG. 12 is fragmentary sideelevation, partly in section, taken substantially along the line l2l2 in FIG. 6, here depicting particularly the supporting rail construction for the head which permits of movement of the head from a position above one conveyor to a position above the adjacent conveyor.

FIG. 13 is an enlarged plan view, partly in section, taken substantially along the line 13-13 in FIG. 7, and depicting certain of the clamping mechanism utilized to lock the bonding head in position.

FIG. 14 is an enlarged vertical sectional view taken substantially along the line 14-14 in FIG. 13, with cer tain parts removed for purposed of clarity, and illustrating the general relationship of parts in the bonding head.

FIG. 15 is a vertical elevational view, partly in section, similar to FIG. 14, but here taken substantially along the line 15-l5 in FIG. 13 and at right angles to the view depicted in FIG. 14.

FIG. 16 is an enlarged fragmentary vertical sectional view depicting the lower end of the apparatus shown in FIG. 14, but here greatly enlarged to show details of the component parts of the equipment including the electrode cooling system and the inert gas flow system utililzed to minimize oxidation.

' FIG. 17 is a fragmentary perspective view of a portion of a battery, here depicting, in both the bonded and unbonded states, battery post/bushing combinations both with and without intercell connectors.

FIG. 18 is a vertical sectional view, here illustrating an adapter embodying the features of the present invention mounted on the lower end of a positive displacement bonding apparatus; the adapter enabling the formation of a bond in accordance with the invention between a battery post and bushing in the absence of an intercell connector.

FIG. 19 is a fragmentary vertical side elevational view, partly in section, here illustrating the second stage of a two stage bonding operation wherein an intercell connector is in position in readiness to be bonded to the previously bonded battery post/bushing combination.

SUMMARY OF THE INVENTION The present invention pertains to apparatus which is intended to overcome all of the aforementioned disadvantages and to provide a system which is capable of performing successive fusion casting and/or fusion bonding operations on a relatively .high speed, mass production or assembly-line basis, yet where each bond formed is essentially devoid of flaws or imperfections and is comparable in quality to the most perfectly formed hand-burned or hand-torched bond heretofore attainable be even the most skilled personnel. To accomplish this, the present invention contemplates novel apparatus wherein a heated ram-like electrode is moved co-axially through a reservoir defining means which, in the exemplary forms of the invention, comprises a co-axial barrel surrounding the electrode and defining therebetween an annular reservoir. An adapter is first placed on the lower end of the reservoir defining meanse.g., the barreland is bottomed on one of the elements to be bonded in a position co-axial with the axis of the bond to be formed. Thereafter, the ram-like electrode is moved axially through the reservoir defining means into engagement with the workpiece or workpieces to be bonded where the heat developed serves to convert the solid workpiece(s) to a molten state in the area selected for the fusion bond.

Continued axial advance of the electrode serves to progressively melt the portions of the workpieces along the axis of the bond area, which axis, of course, coincides with the axis of the electrode, and the molten material thus formed is displaced by the electrode in an annular column surrounding the electrode and within the reservoir defined between the electrode and the selected reservoir defining means.

When the ram-like electrode'reaches the limit of its advance movement, a limit that may be adjusted by the operator to provide for a bond of any desired depth, a short dwell period is provided to insure uniform heating of those portions of the workpieces immediately adjacent the cavity formed therein by-displacement of molten material, as well as to insure uniform heating of the molten material surrounding the electrode and confined within the reservoir. Upon conclusion of such dwell period, the ram-like electrode is retracted from the workpieces and is moved axially through the reservoir defining measn to a position out of contact with the molten material. As a result of such axial retraction of the electrode, the molten material is free to return to the cavity formed in the workpieces during the advance movement of the electrode, where such material is permitted to cool and solidify, thus forming a uniform fusion bond between the workpieces along the entire axis of electrode movement therethrough. Finally, the reservoir defining means-cg, the barrel co-axial with the electrodeis retracted from its bottomed engagement with the workpieces, and a bond cycle is complete. The adapter is then removed, the electrode may be replaced with one of a different configuration. and the above cycle repeated to bond still other workpieces to the first formed bond.

When dealing workpieces formed of conductive metals, the activating circuit for the system is preferably from a suitable power source, through the movable electrode, through the conductive metal workpieces,

through the reservoir defining means, and back to the source. The power source may be either continuous or pulsating. When dealing with non-conductive workpiece materials, the movable ram-like electrode may simple comprise or contain a suitable resistance element or the like capable of attaining and maintaining a desired temperature level sufficient to melt that portion of the workpiece material which is to be displaced and subsequently returned to effect the desired fusion bond.

While the present invention is susceptible of various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and will herein be described in detail. More specifically, the invention will hereinafter be described in connection with equipment for forming leadto-lead bonds and/or for positive displacement bonding of lead, techniques that are particularly suitable for use in the industrial motive-power battery battery industry and, for that reason, the exemplary forms of the invention are described in connection with the making of such batteries. In its broadest aspects, however, it will be understood as the ensuing description proceeds that the invention may fing many other applications outside of the battery making industry, outside of lead-to-lead fusion bonding techniques and, inded, outside of metalto-metal fusion bonding techniques. Therefore, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but, on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as expressed in the appended claims.

THE ENVIRONMENT OF THE INVENTION As hereinabove explained, the present invention will be described herein in connection with methods and apparatus which find particularly, but by no means exclusive, application in the industrial motive-power battery industry. Accordingly, and as best seen by reference to FIGS. 1, 2 and 3 conjointly, there have been depicted fragmentay portions of a typical industrial battery, generally indicated at 50 in FIG. 2, which is here composed of a plurality of individual battery cells 51. Such batteries may vary widely in size, configuration and electrical characteristics, and may, merely by way of example, range upwards of several feet in length, heighth and width and weigh upwards of several tons. Conversely, such batteries may be relatively small and may be capable of being transported by hand.

Referring more specifically to FIG. 1, a conventional battery cell 51 has been depicted in partially exploded form so as to expose most of the various battery components contained therein. Such components normally include a cell casing 52, commonly called a jar, and cover 54, both of which have heretofore conventially been formed of high impact rubber. Contained within the cell casing 52 are a group of negative plates 55, a group of positive plates 56, and a group of separators 58. The negative plates 55 and positive plates 56 of the exemplary cell 51 comprise cast lead grids into which selected chemical pastes, or active materials, are inserted. Generally, a negative plate 55 may contain a paste consisting of a spongy lead material containing an expander to maintain the spongy condition, while the positive plate 56 may contain a paste consisting of lead oxide, sulfuric acid and water mixed to a putty-like consistency. After the pastes have been applied to the respective grids, the grids are dried. The positive plates 56 are normally wrapped with fiberglas or the like (not shown) to insure retention of the active materials, and each positive plate is then inserted into a plastic protective envelope, as best indicated at 59 (FIG. 1 The separators 58 are preferably formed of microporous rubber which is temperature and acid resistant, and are generally flat on the side adjacent the negative plate and grooved on the side adjacent a positive plate. Such separators 58 serve as insulators between the interleaved positive and negative plates, although they are sufficiently porous to permit free passage of electrolyte therethrough.

After casting of the positive and negative plates, application of the active materials thereto, drying, and wrapping of the positive plates, positive and negative groups or assemblies of plates are formed, commonly by welding the lug portions 55a, 56a of the plates to battery straps and/or battery posts. As here shown, the negative plate lugs 55a are welded to a battery strap 60 integral with a pair of vertically upstanding, negative battery posts 61, while the positive plate lugs 56a are welded to a similar battery strap 62 integral with a pair of vertically upstanding positive battery posts 64. The thus assembled negative and positive plate groups are then interleaved with one another, there being a separator 58 between each positive and negative plate, and the entire assembly is inserted into the cell casing orjar 52 on top of a sediment bridge (not shown). A protective element 65, which may be made of plastic, is placed on top of the plate assembly so as to prevent: (1) foreign materials from entering the cell; (2) damage to the internal cell components by careless use of hydrometers or thermometers; and (3) moss shorts between the positive and negative plates. The high impact rubber cover 54 is then positioned on top of the jar or casing 52, with the posts 61 and 64 passing through lead bushings 66 molded in place in the cover, and the cover is secured to the jar by means of a hot, pliable, asphalt based compound. Normally at this stage of the assembly operation, the battery posts 61, 64 are bonded to the respective bushing inserts 66 by a handburning' or hand-torching technique, electrolyte is added to the battery cell through a fill opening 68 adapted to be closed by a screw-threaded tap 69, and the cell is then repetitively charged and discharged to assure proper capacity and quality.

Once the cells 51 have been assembled, charged and inspected, they are then ready to be assembled in various configurations to provide a complete battery 50 to meet specific requirements of a customer or ultimate user. In such assembly, multiple cells are inserted into a steel battery casing 70 (FIG. 2) and interconnected in accordance with the requirements and specifications of the customer or user. Such interconnections commonly entail the use of lead intercell connectors 71 which bridge the space between battery posts of opposite polarity in adjacent cellsi.e., the positive posts of one cell are coupled to the negative posts of an adjacent cell. Referring to FIGS. 2 and 3, it will be observed that each intercell connector 71 is designed so that one end thereof sits on and surrounds a bushing 66 associated with a negative post 61, while the opposite end thereof sits on and surrounds a bushing 66 associated with a positive post 64. The workman then bonds the connector 71 to the post/bushing combination by a conventional hand-burning or hand-torching technique. Thus, referring to FIG. 2, it will be observed that the workman is utilizing a hand-burning technique in which he is holding a carbon burning tool 72 in his right hand and a rod of lead bar-stock 74 in his left hand. The arrangement is such that the carbon burning tool 72 (which could, of course, be an oxyacetylene torch) is used to melt the inner rim 75 of the opening in the connector 71 surrounding the post/bushing combination and, at the same time, to melt the exposed surface of the previously bonded post/bushing combination, with the molten lead thus formed being mixed or puddled by the hot tip of the tool 72. Additional lead is similarly melted by the tool 72 from the lower end of the supplemental lead rod 74 so as to provide sufficient molten lead to fill the entire cavity within the connector 71 defined by the edge 75 and surrounding the postlbushing combination. Indeed, the workman will commonly place a conventional mold (not shown) about the work area so as to permit the formation of a raised, button-like bond, as best indicated at 76 in FIG. 2.

It should be understood, that while it would be possible to create the aforementioned bond 76 in a single hand-burning or hand-torching operation by applying the tool 72 or torch to the assemblage of parts as shown in FIG. 3, the operation is most normally conducted in two stages-first bonding the post/bushing combination and later bonding the connector 71 to the previously bonded post/bushing combination. One reason for such two-stage bonding or torching procedure is simply that it is desirable that a permanent bond be created between the post 61 (64) and bushing 66 immediately after assembly and prior to introduction of electrolyte into the cell so as to prevent acid or other foreign materials from becoming lodged in the interface between the post and the bushing.

It will be immediately recognized by those skilled in the art that the hand-burning and/or hand-torching operations herein described have many disadvantages and are frought with dangers. Such procedures are slow, and require skilled personnel to carry them out. As lead is melted and puddled, it tends to cover the surfaces of the parts to be bonded, and extreme care must be taken to insure that all of the mating surfaces or interfaces to be bonded are uniformly heated and rendered moltenotherwise, molten lead contained within the puddle will tend to adhere to a surface which has not been raised to a sufficiently high temperature level, thereby producing an undesirable cold knit rather than a sound molecular fusion bond. Moreover, failure to obtain uniform heating and melting may result in undesirable crevices or minute passages passing through the interface of the parts being bonded, thus creating leakers and giving rise to the danger of electrocapillary pumping action at the positive post. And, of course, if extreme care is not taken, it is relatively easy to overheat the parts. When this occurs, the entire peripheral portion or rim 78 (FIG. 3) of theconnector 71 may be rendered molten, permitting the puddle of lead to spill over the top of the cell, thereby destroying the connector parts and/or permitting burning of, and consequent damage to the rubber cover 54. Finally, because of the problems associated with such overheating, it has heretofore been impractical to use more economical and lightweight materials such as plastic in the formation of cell casings and/or covers because such materials commonly have much lower melting points than the hard impact rubber heretofore used.

POSITIVE DISPLACEMENT BONDING IN ACCORDANCE WITH THE INVENTION A. General Organization of Exemplary Apparatus Referring now to FIGS. 4 through 8 inclusive, there has been illustrated an exemplary apparatus, generally indicated at in FIGS. 4-7, for carrying out the present invention. As here shown, the exemplary apparatus 100 includes a positive displacement bonding head, generally indicated at 101, carried by an overhead suspension system, generally indicated at 102, for movement over and with respect to one or more batteries 50 carried on a pair of parallel, spaced apart, floormounted conveyors 104, 105. The conveyors 104, may be power driven by any suitable means (not shown) and, to permit of ready control thereover, the bonding head 101 is provided with a pair of operator controls 106, 108 (best illustrated in FIGS. 4 and 5) by which the operator can activate the conveyor driving means to move a selected conveyor 104, 105 in either a forward or reverse direction, or to stop a selected conveyor in a desired location with a battery 50 disposed beneath the bonding head 101. Preferably the operator control 106 forms part of a suitable activating circuit (not shown) for conveyor 104, while control 108 forms part of an activating circuit for conveyor 105. To facilitate placement of batteries 50 on, and removal from, the conveyors, the batteries may be positioned on pallets 109 or the like which can be readily moved'from place to place by conventional fork-lift trucks.

A-l. X-Oriented Movement In order to permit of facile movement of the bonding head 101 over a stationary battery 50 so as to enable the formation of successive bonds at multiple battery post locations on a rapid, production-line basis, the overhead suspension system 102 is preferably designed to permit of movement of the bonding head in both an X-oriented direction (transversely of the conveyors as indicated by the arrows in FIGS. 4-7) and a Y-oriented direction (along the line of conveyor movement as indicated by the arrows in FIGS. 4-6). To accomplish this,

the overhead suspension system 102 includes a pair of parallel, spaced apart beams 110, 111 (best illustrated in FIGS. 4 and 12) which extend transversely across both conveyors 104, 105 and which are connected at their opposite ends by cross beams 112, 114 (FIG. 6); the beams 110, 111, 112 and 114 defining a generally rectangular support structure (FIG. 6). Vertically disposed, upright stanchions 115 and 116 are permanently affixed at their upper ends to the cross beams 112, 114 respectively, and are mounted on the floor outboard of the conveyors 104, 105. The beams 110, Ill respectively support guide rails or tracks 118, 119 which are parallel to the beams and also extend transversely across the conveyors 104, 105. A carriage assembly, generally indicated at 120 in FIGS. 4 and 7, is provided with suitable bearing sleeves 121 (FIGS. 4 and 12) mounted in surrounding relation to the rails 118, 119, thereby permitting slidable movement of the entire carriage assembly 120 in an X-oriented direction along the rails. Suitable lubricating means (not shown) may be provided so as to minimize friction and thereby permit ease of movement of the carriage assembly l20-along the rails.

A-2. Y-Oriented Movement For the purpose of permitting movement of the bonding head 101 in a Y-oriented directioni.e., along the path of movement of the conveyors 104, 105-the carriage assembly 120 is provided with a pair of depending support beams 122, 124 (best illustrated in FIG. 4) which here serve to support Y-oriented tracks or guide rails 125, 126, respectively. A sub-carriage assembly, generally indicated at 128, is slidably supported on the guide rails 125, 126 by means of bearing sleeves 129. Again, suitable lubricating means (not shown) may be provided for minimizing frictional resistance between the rails 125, 126 and bearing sleeves 129 so as to permit relatively easy movement of the sub-carriage assembly 128 along the Y-oriented guide rails 125, 126.

A-3. Z-Oriented Movement In carrying out the present invention, provision is made for enabling vertical movement of the bonding head 101 along a Z-oriented axis as viewed in FIGS. 4, and 7. To this end the various operating parts of the bonding head 101 are carried by a base plate 130 which is secured to the lower ends of a pair of vertically disposed support shafts 131, 132, such shafts passing upwardly through respective ones of a pair of bearing sleeves 134, 135 rigidly secured to a plate 136 which forms the undercarriage of sub-carriage assembly 128. The upper ends of the shafts 131, 132 have enlarged collars 138, 139 (FIG. 6; best illustrated in FIG. 14) respectively affixed thereto which serve as stops engageable with plate 136 to limit downward movement of the bonding head 101.

For the purpose of permitting the bonding head 101 to float during periods between bonding cycles and during movement of the head by the operator, and to further permit automatic movement of the operating parts of the bonding head during a bonding cycle, the illustrative apparatus is provided with a series of fluidoperated, preferably pneumatic, piston/cylinder combinations 140, 141, 142 the specific functions of which will hereinafter be described in somewhat greater detail and which are described in considerably greater detail in the aforesaid copending applications of Robert Holbrook Cushman, Ser. No. 435,157, and Raymond L. Schenk, .Ir., Ser. No. 435,178. Those interested in such more detailed descriptions are referred to the aforesaid copending applications. For the purpose of the present description of the general organization of parts for the exemplary apparatus, it will suffice to say that the opposite sides of the piston within piston/cylinder combination 140 are pressurized so as to balance the weight of the components carriedby'base plate 130 and which comprise the bonding head 101, thereby permitting the head to float at whatever height or level it is positioned in.

A4. Operator Controlled Positioning of Bonding Head The arrangement is such that when the operator wishes to move the bonding head 101 into a position in readiness to initiate a bonding cycle-for example, in readiness to bond a battery post/intercell connector combination such as generally indicated at 144 in FIGS. 4 and 5-it is merely necessary that he first activate the control 106 for conveyor 104 (or, alternatively, control 108 for conveyor to generally locate a battery 50 beneath the bonding head 101. Having generally located a battery relative to the head, the operator next grasps one of the handles 145 projecting laterally from the base plate and shifts the bonding head 101 laterally in either or both of an X-oriented and/or Y-oriented direction until the bonding ram assembly, generally indicated at 146 in FIGS. 4, 5 and 7, is accurately centered over the particular battery post- /intercell connector combination 144 to be bonded. The operator then needs only push downwardly on the handle so as to urge the bonding head 101 and ram assembly 146 downwardly from the position shown in FIG. 7 to the position such as shown in FIGS. 4 and 5 where the particular battery post to be bonded projects co-axially upward into the bonding ram assembly 146 when the latter is bottomed on the intercell connector to be bonded. The operator is now ready to initiate a bonding cycle for the particular post/connector combination 144 located under the bonding ram assembly 146 and, when the bond is completed, the bonding head 101 will automatically move upward to the position shown in FIG. 7. The operator then again grasps the handle 145 and moves the bonding head 101 in ei ther an X- or Y-oriented direction to a position over the next post/connector combination 144 to be bonded, and again repeats the foregoing operation.

A-S. Typical Battery Post, Bushing and Intercell Connector to Be Bonded Referring next to FIGS. 9 and 10, there have been illustrated details of a typical organization of battery components particularly suitable for bonding in accordance with the present invention. More specifically, there is depicted a battery post/intercell connector combination 144 which consists of an upstanding lead battery post 148, a lead cover bushing 149 adapted to be molded directly into a battery or cell casing 150 (which may conveniently be made of plastic, hard impact rubber, or any other suitable material), and a lead intercell connector 151. The lower end of battery post 148 is, as heretofore described, affixed to, or integral with, a battery plate strap 152 which serves to interconnect a plurality of battery plates of like polarity-either positive plates or negative plates. The arrangement is such that, when assembled prior to bonding as shown in FIG. 10, the battery post 148 passes co-axially upward through the lead bushing insert 149 and cover 150. The opposite ends of the lead intercell connector (on such end being visible in FIGS. 9 and 10) are each provided with a vertically disposed opening or passage 154 having a diameter sufficiently large to permit the connector 151 to be positioned in co-axial surrounding relation to an upstanding flange 155 formed on the bushing 151, with the lower surface of the connector in direct lead-to-lead contact with a horizontal or radial flange 156 formed on the bushing.

To insure concentricity of the parts and, at the same time, to provide for sound electrical contact therebetween, the lead battery post 148 may be provided with two or more slightly raised locating ribs or projections (one such rib having been illustrated at 158 only in FIG. 9), which ribs have a slightly larger diameter than the inside diameter of the bushing 149. However, because of the characteristic of softness inherent with leadathe battery post may be relatively easily force- I fit into the bushing 149, and the presence of such ribs 

1. A method of bonding n (where n equals three or more) component parts together in a two-stage bonding operation comprising the steps of: a. positioning n-x (where x equals at least two less than n) components parts on a work axis; b. locating a bonding head over the n-x component parts with said bonding head having a ram disposed on the work axis and a barrel surrounding the ram; c. positioning an adaptor assembly on the lower end of the barrel with the assembly defining an annular barrel extension having a smaller internal diamter than the barrel; d. moving the ram, barrel and adaptor assembly into engagement with the n-x component parts; e. heating the ram to a temperature sufficient to convert those portions of the n-x component parts in the path of relative ram movement to the molten state; f. moving the heated ram through the barrel, adaptor assembly, and n-x components parts so as to cause the ram to melt the material in its path of relative movement to a desired depth in the n-x component parts with the molten material thus formed being displaced by the ram from the area of ram penetration into the material and shifted therefrom into the barrel; g. retracting the ram from engagement with the n-x component parts from its position of maximum penetration so as to cause the ram to be withdrawn from such parts; h. returning the molten material theretofore displaced into the barrel back to the area of ram penetration into the n-x component parts where such molten material is permitted to cool and solidify; i. retracting the barrel; j. removing the adaptor assembly from the barrel; k. positioning said x component parts on said work axis in abutting relation to said n-x component parts; l. advancing said barrel and said ram into engagement with said n component parts; and, m. again heating, advancing and retracting said ram so as to melt those portions of said x component parts in the path of ram movement and to remelt those portions of the n-x component parts in the path of ram movement and to thereby bond said x and said n-x component parts together.
 2. The method as set forth in claim 1 wherein said n-x component parts comprise a lead battery post and a lead cover bushing, and includes the preliminary step of inserting the battery post coaxially through the cover bushing, and said x component part comprises a lead battery intercell connector having an end opening therein for receiving the battery post and cover bushing and step (k) includes positioning said intercell connector with said opening coaxially surrounding said battery post and cover bushing.
 3. Apparatus for bonding n (where n is equal to three or more) meltable component parts together by a two-stage positive displacement molecular fusion bonding process, said apparatus comprising, in combustion: a. means for supporting said n-1 meltable component parts on a work axis; b. a fRame; c. a bonding head carried by said frame in a position overlying the component parts; d. a barrel carried by said bonding head for movement along said work axis into sealing engagement with the component parts to be bonded; e. a ram carried by said bonding head for movement along said work axis, said ram being coaxial with said barrel and capable of axial movement therethrough; f. an adaptor assembly releasably clamped to the lower end of said barrel and defining therewith an annular barrel extension having a smaller internal diameter than the diameter of said barrel; g. means for advancing said barrel, adaptor assembly, and ram into engagement with said n-1 component parts; h. means for heating said ram to a temperature sufficiently high to melt and form a cavity in those portions of the n-1 component parts in the path of ram movement; i. ram advancing means for positively displacing the moltem material formed by engagement of said ram with the component parts into said barrel and storing the molten material therein in heat transfer relation with said heated ram; j. means for axially retracting said ram from said n-1 component parts so as to enable the displaced molten material stored in said barrel to flow back to said cavity where said material is permitted to cool and solidify to form a uniform molecular fusion bond between said component parts with said bond being coextensive with the degree of penetration of said ram into said component parts; k. means for axially retracting said barrel from engagement with said component parts following cooling and solidification of said molten material; l. means for removing said adaptor assembly from said barrel; and, m. means for again advancing said barrel and said ram into engagement with said n component parts so as to bond all of said n parts together including said n-1 parts.
 4. Apparatus as set forth in claim 3 further characterized in that an electrically insulating liner is mounted within said adaptor assembly to preclude a direct current path between said adaptor assembly and the ram when the latter passes axially therethrough.
 5. Apparatus as set forth in claim 4 further characterized in that said liner includes an upwardly projecting lip dimensioned to extend upwardly into the barrel of the bonding apparatus. 